Ectoparasites such as fleas, lice, flies, mosquitoes, ticks, and mites, and endoparasites such as digestive tract nematodes, trematodes, and heartworms are problematic to both humans and animals. Such parasites include an egg stage, a larval stage, a pupal stage, a nymph stage, and an adult stage, decrease the body weight increase of a host, cause low quality of leather, wool, and meat, cause death in some cases, and exert a serious influence on productivity in the domestic animal industry. In addition, ectoparasites and endoparasites spread disease through food or pets, and cause discomfort. In particular, it is known that ectoparasites cause infection by becoming the habitat for various microbial pathogens including bacteria, viruses, and parasitic protozoa. Many ectoparasites are pathogenic with respect to humans, and other homoiothermal mammals and birds. Examples of diseases in which ectoparasites are involved include malaria, lymphatic filariasis, and blood-borne filariasis, trachoma, trypanosomiasis, leishmaniasis, Rocky Mountain spotted fever, Lyme disease, babesiosis, and food-borne diseases caused by salmonella, E. coli, or Campylobacter, but the examples thereof are not limited thereto.
An important point in medical care against parasite by parasite exterminating drugs is to promote the development of a reagent capable of suppressing the parasite. For example, usual methods for suppressing parasite by parasite exterminating drugs, in general, focus on the use of an agricultural pesticide, and these are unsuccessful or insufficient in many cases for at least one of the reasons described below. The reasons are (1) the owner or the applicator's compliance (frequent administration is required) failure, (2) behavior or physiological intolerance of an animal with respect to the exterminator product or the administration method, (3) expression of resistance of ectoparasites with respect to a reagent, or (4) a negative effect with respect to the environment and/or toxicity.
Specifically, it is known or considered that ticks and fleas are parasitic on wild animals in the same manner as on domestic animals or humans, and are involved in mediating pathogens including bacteria, viruses, and parasitic protozoa. Currently, ticks are considered to be the second most common vectors of human diseases in the world after mosquitoes; however, in North America, ticks are considered to be the most serious pathogens. Since there is often a need to treat the environmental reservoir host together with the direct host at the same time, effective extermination against parasite by ectoparasites such as fleas in the domestic environment is difficult and unrealistic in many cases. Currently, suppression of ticks in the agricultural environment is performed by an overall harmful organism treatment method in which various suppression methods are adapted to one region or one type of tick, while sufficiently considering the environmental effect.
Although the use of insecticides and exterminators is beneficial to suppress ectoparasites, improved compounds, formulations, and methods to replace the existing ones are needed. Desirable compounds, formulations, and methods will not only provide alternative treatments but also overcome at least some of the restrictions of current methods. Such restrictions include toxicity and safety to an animal, a user, or an owner, restrictions relating to the efficacy (potency, durability of activity, killing speed), and the problem of resistance (limited to this). In addition, affecting the beneficial use of insecticides and exterminators is hindrance of administration, and as such hindrance, the method, a user or an owner's compliance problem relating to the treatment recommendation, and repetition of administrations are exemplified. For example, excessively repeatedly treating animals is often troublesome and difficult for a user or an owner, and therefore, it is desirable to reduce the number of administrations while maintaining the efficacy.
Specific examples of the 1-heterodiene compounds used in the ectoparasite control agent of the present invention are disclosed in PTLs 1 and 2.